$OpenBSD: patch-sendip_c,v 1.1 2016/12/05 13:57:20 jca Exp $
--- sendip.c.orig	Fri Dec 26 15:31:29 2014
+++ sendip.c	Tue Nov 22 03:17:46 2016
@@ -111,7 +111,11 @@ void send_ip (char* src, char *dst, char *data, unsign
 		(struct sockaddr*)&remote, sizeof(remote));
 	
 	if (result == -1 && errno != EINTR && !opt_rand_dest && !opt_rand_source) {
+		int save_errno = errno;
 		perror("[send_ip] sendto");
+		if (save_errno == EHOSTUNREACH)
+			printf("[send_ip] "
+			    "Note that PF might be blocking your packets.\n");
 		if (close(sockraw) == -1)
 			perror("[ipsender] close(sockraw)");
 		if (close_pcap() == -1)
